Question: In the right triangle shown, $AC = 4$ and $AB = 6$. What is $BC$ ? $A$ $C$ $B$ $4$ $?$ $6$
Answer: We know $a^2 + b^2 = c^2$ We want to find $a$ ; let $b = 4$ and $c = 6$ So $a^2 = c^2 - b^2 = 6^2 - 4^2 = 20$ Then, $a = \sqrt{20}$ Simplifying the radical gives $a = 2\sqrt{5}.$